Field of Invention
The present disclosure relates to an electronic circuit substrate and a method of manufacturing the electronic circuit substrate. More particularly, the present disclosure relates to a metal substrate and a method of manufacturing the metal substrate.
Description of Related Art
A printed circuit board is an indispensable material in electronic products. A demand of the printed circuit board is increased with a growing demand of consumer electronic products. A flexible printed circuit board is flexible and can be three-dimensionally wired, and thus is widely applied recently in computers and its peripheral equipment, communication products and consumer electronic products under a development trend of a compact size and flexibility of technical electronic products.
A typical printed circuit board is a composite substrate constituted by a dielectric substrate, such as resin, glass fiber or other plastic materials, a conductive layer with high purity, such as copper foil or other metal material layers. For example, a flexible copper clad laminate is constituted by a polyimide (PI) substrate as the dielectric substrate, and a non-adhesive single-sided copper foil coated or bonded on the PI substrate using a casting method or a lamination method.
Recently an electronic system towards a direction of a compact size and low cost, and thus the flexible printed circuit board towards a direction of ultra-thin, high density and multifunction. However, fold injury, pad injury or delamination (or called as blistering) may occur on a single layer PI substrate for manufacturing an ultra-thin flexible printed circuit board during processing due to inadequate stiffness of the substrate, and thus to affect production yield and dimensional stability. For this reason, an adhesive layer formed on a surface of the single layer PI substrate using a coating method or a transfer printing method and a reinforcing layer overlying the adhesive layer are provided, and a lamination is then performed to let the reinforcing layer tightly adhere to the PI substrate to obtain a composite structure and to reinforce the ultra-thin copper clad substrate, and thus to increase yield thereof.
However, during the thermal lamination with high temperature and high pressure, the adhesive may be fused and bonded to the PI substrate. The adhesive may be remained during the reinforcing layer is tore off, which results in increasing of product defect rate. If the reinforcing layer is retained, the thickness of the flexible printed circuit board is increased. Therefore, there is a need for an advanced printed circuit board and a method of manufacturing the same to solve problems in prior art.